Background
Inflammation is now recognized to play a key role in the pathogenesis of atherosclerotic cardiovascular disease. Two circulating markers of inflammation, C-reactive protein (CRP) and interleukin (IL)-6, have emerged as predictors of future cardiovascular pathology and mortality in epidemiologic studies of (middle aged women) midlife healthy men and women, postmenopausal women, and older adults.
The aim of the present study was to study the changes in IL-6 in acute coronary syndrome (ACS) and to clarify whether IL-6 release is a factor initiating the inflammatory process in ACS or whether it is predominantly a response to this clinical condition, and to assess its correlation with CRP, cardiac biomarkers troponin I, and CK-MB for risk prediction in ACS.
Patients and methods
The study included 60 patients admitted by ACS who were categorized randomly into three groups: group I included 20 patients admitted for unstable angina, group II included 20 patients admitted for ST-segment elevation myocardial infarction with successful thrombolytic therapy, and group III included 20 patients admitted for ST-segment elevation myocardial infarction with failed thrombolytic therapy. The study also included 12 healthy control patients matched for age and sex (group IV). Blood levels of IL-6, CRP, and cardiac troponin I were measured; all samples of groups II and III were obtained after thrombolytic therapy whereas samples of group I were obtained on admission.
Results
IL-6 was significantly higher in group II, with a mean of 87.10, and ranged from 3.0 to 550.0; on exclusion of two patients who had an IL-6 level of 220 and 550 we obtained a mean of 54. In group III, the mean level was 52.36, ranging from 5.0 to 120.0, compared with control group IV, in which it ranged from 3.0 to 5.0, mean 3.67 (P < 0.001*). There was a positive correlation between IL-6 and CRP levels in group I (r = 0.385, P = 0.094) and group II (r = 0.166, P = 0.483), but this was statistically nonsignificant, and in group III, there was a statistically significant correlation (r = 0.638, P = 0.0002). IL-6 serum levels did not correlate with cardiac troponin levels in any of the patient groups I (r = 0.049, P = 0.836), in group II (r = 0.151, P = 0.524), and in group III (r = 0.079, P = 0.741). IL-6 did not correlate with any of the risk factors such as history of IHD, HTN, DM, and smoking. There was no statistically significant correlation between IL-6 and complications, except for the development of shock. The CRP level was significantly increased in ACS in comparison with the control group. CRP showed a significant increase in group III, ranging from 10.70 to 181, mean 84.25, and ranging from 2.47 to 155, mean 54.37 in group II compared with a mean level of 50.44 in group I and a mean of 1.96 in the control group, group IV (P = 0.0001*).
Conclusion
Atherosclerosis is currently considered a systemic inflammatory disease and IL-6 is an inflammatory cytokine. The IL-6 serum level was significantly increased in patients with ACS and in patients with successful thrombolytic therapy. There was a statistically significant positive correlation between IL-6 and CRP in ACS patients with failed thrombolytic therapy; IL-6 serum levels did not correlate with cardiac troponin levels in any of the ACS patient groups.